The present invention disclosed herein relates to an optoelectronic device and a method of fabricating the same, and more particularly, to a superluminescent diode with a high optical power and a broad wavelength band, and a method of fabricating the same.
The present invention has been derived from research undertaken as a part of the information technology (IT) development business by Ministry of Information and Communication and Institute for Information Technology Advancement in the Republic of Korea (Project management No.: 2006-S-004-02, Project title: silicon based high speed optical interconnection IC).
A superluminescent diode (SLD) is an optical device capable of providing several advantages such as a high optical power, a wide optical bandwidth, and a low spectral modulation. Therefore, the SLD is used as a light source for an optical gyroscope, a test of a wavelength-division multiplexing (WDM) system, an optical coherence tomography (OCT), and a fiber-optic sensor.
Like a laser diode, the SLD uses optical amplification phenomena by stimulated emission to achieve high optical power. In order to achieve a wide optical bandwidth, however, the SLD should be configured to reduce optical resonance phenomena, which differs from the laser diode. Accordingly, the SLD has much higher optical power (that is, close to an optical power of a laser diode) than a light emitting diode (LED), and also has much broader optical bandwidth than a laser diode.
A typical structure of the SLD is similar to that of a laser diode, but its reflective surfaces constituting a resonator have a relatively low reflectivity so as to reduce optical resonance phenomena. To reduce the reflectivity of the reflective surface in the SLD, there are provided various methods, for example, an antireflection coating technique, a method of providing an absorption region, or a method of forming an oblique reflective surface.
In addition, other typical methods for increasing a wavelength bandwidth have been proposed. As one of the typical methods, U.S. Pat. No. 6,184,542 (Alphonse et al., “superluminescent diode and optical amplifier with extended bandwidth”) discloses a method of attaching active layers with different wavelengths along a direction of an optical waveguide. As another typical method, a method of using quantum well intermixing technique has been proposed in a paper by Ong et al. (“High performance quantum well intermixed superluminescent diode”, Measurement Science and Technology, vol. 15 (2004), pp. 1591-1595). However, these methods may increase a wavelength bandwidth of the SLD, but have a limitation in that it is difficult to provide a required high optical power. For example, the optical power of the SLD according to the paper of Ong et al. is excessively low, e.g., about 1.5 mW.